package com.jacklei.ch15;


/*
* 给定一个二叉树，判断它是否是高度平衡的二叉树。

本题中，一棵高度平衡二叉树定义为：

一个二叉树每个节点 的左右两个子树的高度差的绝对值不超过 1 。

 

示例 1：


输入：root = [3,9,20,null,null,15,7]
输出：true
示例 2：


输入：root = [1,2,2,3,3,null,null,4,4]
输出：false
示例 3：

输入：root = []
输出：true
 

提示：

树中的节点数在范围 [0, 5000] 内
-104 <= Node.val <= 104

来源：力扣（LeetCode）
链接：https://leetcode.cn/problems/balanced-binary-tree
著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。*/
public class BalancedBinaryTree {
    public static void main(String[] args) {
        BalancedBinaryTree b = new BalancedBinaryTree();
        TreeNode treeNode = new TreeNode(1);
        treeNode.left= new TreeNode(21);
        treeNode.right= new TreeNode(22);
        treeNode.left.left= new TreeNode(31);
        treeNode.left.right= new TreeNode(32);
        treeNode.left.left.left= new TreeNode(41);
        treeNode.left.left.right= new TreeNode(42);
        System.out.println(b.isBalanced(treeNode));

    }
    public boolean isBalanced(TreeNode root) {
        if(root == null) return true;
        return f(root).isBalanced;
    }

    public Info f(TreeNode root){
        if(root == null) return new Info(0,true);
        Info left = f(root.left);
        Info right = f(root.right);
        System.out.println(root.val);
        if(left.isBalanced == false || right.isBalanced ==false){
            return new Info(-1,false);
        }
        boolean isBalanced = false;
        if(Math.abs(left.curHigh - right.curHigh)<= 1){
            isBalanced =  true;
        }

        return new Info(Math.max(left.curHigh , right.curHigh)+1,isBalanced);
    }
    class Info{
        int curHigh;
        boolean isBalanced;

        public Info(int curHigh, boolean isBalanced) {
            this.curHigh = curHigh;
            this.isBalanced = isBalanced;
        }
    }

    public static class TreeNode {
      int val;
      TreeNode left;
      TreeNode right;
      TreeNode() {}
      TreeNode(int val) { this.val = val; }
      TreeNode(int val, TreeNode left, TreeNode right) {
          this.val = val;
          this.left = left;
          this.right = right;
      }
  }
}
